There is renewed speculation that Bashar al-Assad might be offered exile as a way out of the impasse. Photograph: Eric Gaillard/Reuters

Russia and western countries are locked in diplomatic arm-wrestling over demands that Syria's president, Bashar al-Assad, hands over power to his deputy as part of a UN-backed Arab plan for a peaceful solution to the country's bloody crisis.

The latest draft of a resolution being submitted to the UN security council, and being discussed by ambassadors in New York late on Thursday, has dropped an explicit demand that Assad bows out but still fully supports the "political transition" sought by the Arab League. The change is triggering concerns that the resolution could be drastically watered down to secure agreement.

Diplomatic sources said the main problem was Russian concern that the league plan constituted regime change by another name. "Moscow is looking to fudge this issue of political transition," said one western official.

Language could be further softened during the negotiations, with Britain and other western countries signalling satisfaction with a Russian abstention.

The draft UN resolution now looks unlikely to be put to a vote on Friday, pending a crucial meeting of Russia's national security council in Moscow. China is also being tougher than expected.

Talk of a political transition has also fuelled renewed speculation that Assad might be offered exile as a way out of the impasse, with Arab and western reports suggesting that the United Arab Emirates was one possible option.

Similar ideas surfaced about Muammar Gaddafi during last year's Libyan crisis, but came to nothing.

New language in the latest UN draft states categorically that the intention is to resolve the Syrian crisis "without foreign military intervention", emphasising the point to assuage Moscow's concerns about a repeat of what happened in Libya.

In a further change the resolution is less emphatic about holding Syria to account for implementation, hinting that the anti-Assad camp might also need to comply.

Another innovation is praise for a Russian offer to host a conference of the Syrian government and opposition. But the main opposition groups say they have no faith in talks after 10 months of bloodshed in which, the UN says, 5,400 people have been killed.

The revised draft also removes a call on UN member states to act to prevent the flow of arms into Syria; another clause opposed by Russia, which has maintained the Soviet Union's policy of being a big arms supplier to the Assad regime. Moscow has repeatedly made clear that it plans to continue delivering weapons.

Some Syrian opposition figures fear there will arise a UN resolution so bland and based on the lowest common denominator that it will be almost worthless, achieving international unity at the price of being stripped of meaningful content.

Burham Ghalioun, head of the Syrian National Council, the main exiled opposition group, has met Russia's UN envoy to make his case.

Malik al-Abdeh, director of Barada TV, a Syrian opposition channel, said: "The SNC have put all their eggs in the basket of the Arab League so they are going along with what it is doing. They don't have the leverage to torpedo these efforts even if they are detrimental to their cause."

Western governments say they believe that the most desirable outcome in New York is a watered-down UN resolution that the Russians do not veto, rather than a more robust one that they block.

The Syrian Revolution General Commission reported 13 people killed by security forces on Thursday.

Human Rights Watch urged the UN to apply greater pressure on Syria. "After 10 months of passivity, during which more than 5,400 people have been killed by Syrian security forces, security council members should have run out of excuses for inaction," said Philippe Bolopion, UN director at HRW. "Any country should be wary of supporting the position of Russia, which is signing lucrative arms deals with the Syrian government while providing it with diplomatic cover."

Russia and China, which both have vetoes, are also being supported by India, Pakistan, and South Africa, non-permanent members of the council.